Most Popular Indexes

All About the Basics of Indexes in Oracle 12c

An index is a simple concept. It is typically a listing of keywords accompanied by the location of information on a subject. To find information on indexes, for instance, you look up the word “indexes” in the index at the back of this book. It will give the number of the page you are reading […]

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How to Create a Bitmap Index in Oracle 12c

To help tune queries that use non-selective columns in their limiting conditions, you can use bitmap indexes. Bitmap indexes should only be used if the data is infrequently updated because they add to the cost of all data-manipulation transactions against the tables they index. NOTE Bitmap indexes should not be used for tables involved in […]

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Tips on Indexed Columns in Oracle 12c

Traditional (B*-tree) indexes are most useful on columns with a significant amount of variety in their data. For instance, a column that indicates whether a company is a current client with a Y or N value would be a poor choice for a traditional index and could actually slow down a query; a bitmap index […]

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How to Rebuild an Index in Oracle 12c

Oracle provides a fast index rebuild capability that allows you to re-create an index without having to drop the existing index. The currently available index is used as the data source for the index, instead of the table’s being used as the data source. During the index rebuild, you can change its STORAGE parameters and […]

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Improving Performance with MySQL Index Columns

In addition to creating new indexes to improve performance, you can improve database performance with additional schema optimizations. These optimizations include using specific data types and/or column types. The benefit is a smaller disk footprint producing less disk I/O and results in more index data being packed in available system memory. Data Types Several data […]

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Optimizing MySQL Indexes

The management of indexes—how they are created and maintained—can impact the performance of SQL statements. Combining Your DDL An important management requirement when adding indexes to MySQL is the blocking nature of a DDL statement. Historically, the impact of an ALTER statement required that a new copy of the table be created. This could be […]

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Performance Tuning for MySQL with Indexes

A surprising number of people in online forums request information about slow queries without having tried to add an index to a frequently accessed field. As you know from Chapter 3, tables with fields that are accessed frequently can be ordered by creating an index. An index points to the place on a database where […]

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Using MySQL Indexes

To speed up searches and reduce query execution time, MySQL lets you index particular fields of a table. The term “index” here means much the same as in the real world. Similar in concept to the index you find at the end of a book, an index is a list of sorted field values used […]

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What You Should Know About Limitations in MySQL Indexes

There are several limitations to how indexes are used and managed in MySQL in comparison to other RDBMS products. Cost Based Optimizer MySQL uses a cost based optimizer to prune the possible query tree to create the most optimal SQL execution path. MySQL has limited capabilities for using generated statistics to aid the optimizer as […]

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About MySQL Many Column Indexes

While indexes can contain multiple columns, there is a practical limit in the effectiveness of the index. Indexes are part of the relational model to improve performance. The index row width should be as short as practical in order to provide as many index records per index data page. The benefit is to traverse the […]

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What You Should Know About MySQL Multi Column Indexes

It is possible for an index to have two or more columns. Multi column indexes are also known as compound or concatenated indexes. Let us look at a query that could use two different indexes on the table based on the WHERE clause restrictions. We first create these indexes. mysql> ALTER TABLE album -> ADD […]

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